Ice, Water Stress, and Transboundary Conflict

The largest reservoirs of fresh water on Earth are locked away as ice in the planet's two remaining continental ice sheets. The Antarctic Ice Sheet is by far the largest, holding somewhere around 90 percent of the world's ice and roughly 60 to 70 percent of its fresh water, and is generally divided into two distinct regions: the East Antarctic Ice Sheet, which rests on a large landmass mostly above sea level and has historically been comparatively stable, and the West Antarctic Ice Sheet, which rests largely on bedrock below sea level and is considered significantly more vulnerable to rapid, potentially irreversible loss as warmer ocean water erodes it from below. The Greenland Ice Sheet, though far smaller than Antarctica's, is the second-largest body of ice on the planet and, because it sits at lower latitudes and is exposed to more direct atmospheric warming, has in recent decades become one of the fastest-changing large ice masses on Earth, contributing a substantial and growing share of observed global sea level rise. Were either ice sheet to melt completely, global sea level would rise by many meters, though such a scenario would unfold over centuries to millennia.